This invention relates to cryogenic refrigerators.
Gifford-McMahon and pulse-tube cryocoolers are known sources of cryogenic refrigeration for cooling superconductor devices. Where the superconductor device is rotating, such as in a superconductor motor, a thermal link, for example, a fan, is provided to couple the stationary cryogenic refrigerator to the rotating device.
According to one aspect of the invention, a cryogenic refrigerator for cooling a rotating device includes a stationary regenerator, and a rotatable cold heat exchanger coupled to the stationary regenerator to rotate relative thereto.
Embodiments of this aspect of the invention may include one or more of the following features.
The cryogenic refrigerator is of the Gifford-McMahon type. A stationary cylinder houses the regenerator, and a rotatable cylinder mounted to the cold heat exchanger is concentrically arranged about the stationary cylinder. A filler material is located between the stationary and rotatable cylinders.
In an illustrated embodiment, the rotatable cylinder is axially offset of the stationary cylinder and aligned along a common axis. A stem extends from the regenerator. The cylinders define a flow channel therebetween.
A seal, for example, a ferrofluidic seal, is located between the stationary and rotatable cylinders.
In another illustrated embodiment, the cryogenic refrigerator is of the pulse-tube type with a pulse tube concentrically arranged relative to the regenerator, for example, the pulse tube is concentrically arranged about the regenerator. The cold heat exchanger includes a stationary portion coupled to the regenerator and a rotatable portion coupled to the pulse tube. The stationary and rotatable portions of the cold heat exchanger define a flow channel therebetween, and the stationary portion defines a flow channel. The cold heat exchanger includes screens. The cryogenic refrigerator includes a surge volume housing, an aftercooler, and a warm end heat exchanger. The surge volume housing and the aftercooler define a flow orifice therebetween.
According to another aspect of the invention, a method of cooling a rotating superconductor device includes providing a cryogenic refrigerator including a stationary regenerator and a rotatable cold heat exchanger coupled to the stationary regenerator to rotate relative thereto, and coupling the rotatable cold heat exchanger to the superconductor device.
According to another aspect of the invention, a pulse tube cryogenic refrigerator includes first and second valve assemblies for controlling flow between a compressor and a regenerator of the refrigerator, and a controller for detecting failure in the first valve assembly and switching from the first valve assembly to the second valve assembly.
Embodiments of this aspect of the invention may include one or more of the following features.
Each valve assembly includes a rotary valve including a high pressure flow channel and a low pressure flow channel. Alternatively, each valve assembly includes first and second solenoid valves. The pulse tube cryogenic refrigerator includes a valve, for example, first and second solenoid valves, for switching between the first and second valve assemblies, and first and second differential transducers for measuring pressure across the valve assemblies.
Advantages of the invention include the ability to directly couple the refrigerator to a rotating object to cool the rotating object without having to rotate the refrigerator regenerator. Additional advantages include a back-up valve system providing reliability in case of system failure.
Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.